Sustainability and Interdependence

Question 1

Food security

Answer 1

• sufficient quantity of food available
• provides sufficient nutritious value (quality)
• economic means to access food

increasing issue as human population increases and available land decreases

Question 2

Sustainable foods

Answer 2

foods that can be continually produced without damaging the involved ecosystems

Question 3

Energy loss

Answer 3

Energy is lost between each trophic level (via movement, generating heat, making of undigestible parts and waste products) so only 10 percent is conserved at each stage

Due to this, shorter food chains have a much lesser loss of energy, meaning arable land planted with crops produces far more food than the same land planted with grass to feed livestock

Question 4

Fate of light on leaf

Answer 4

Light is a form of electromagnetic radiation which travels in waves. White light is made up of all colours of the visible spectrum, each colour has a different wavelength.

When white light hits a leaf it has three possible fates:

• Absorbed
• Reflected
• Transmitted

When light is absorbed it is done by different pigments found within the granum (chlorophyll a, chlorophyll b, and the carotenoids [carotene, xanthophyll] )

The chlorophylls are the main pigments. They absorb blue, violet and some red wavelengths of light.

The carotenoids are the accessory pigments. They maximise the amount of wavelengths available to be absorbed (some green/ yellow) and pass the energy they capture onto the chlorophylls.

Absorption spectrum: shows the wavelengths absorbed by each pigment

Action spectrum: shows the rate of photosynthesis at each wavelength

Question 5

Photosynthesis

Answer 5

PHOTOLYSIS stage (occurs in granum of the chloroplast):

• Light energy is absorbed by chlorophyll creating high energy electrons, they are captured by the primary electron acceptor then transferred along an electron transport chain pumping hydrogen ions into grana and releasing energy.
• Some of the energy is used to split water into oxygen (which is given off via stomata) and hydrogen (which is picked up by NADP to make NADPH for the calvin cycle).
• The rest of the energy and hydrogen ions in grana is used by enzyme ATP synthase to build up ADP + Pi to ATP for the calvin cycle.

CALVIN CYCLE/ CARBON FIXATION stage (occurs in stroma of the chloroplast):

• carbon dioxide enters cycle via stomata, and the enzyme RuBisCO causes it to react with RuBP to form 3-phosphoglycerate
• the 3-phosphoglycerate joins with the hydrogen from NADPH (NADPH -> NADP) and is phosphorylated by the addition of an inorganic phosphate (Pi) (ATP -> ADP + Pi + energy), forming G3P
• some G3P is used to regenerate RuBP (and continue the cycle) or to form glucose
• glucose can then be used in respiration, converted into starch (storage carbohydrate), converted into cellulose (structural carbohydrate - cell wall), or used in biosynthetic processes

Question 6

Assimilation

Answer 6

the process by which glucose is converted into complex components (increases the plant’s biomass)

net assimilation = gain in dry mass (as water content of organisms fluctuates) by photosynthesis + loss in mass due to respiration

net assimilation = increase in dry mass per unit leaf area (allows comparison of different samples)

Question 7

Plant productivity

Answer 7

Productivity is the rate at which plants in an ecosystem generate new biomass

Units: unit of biomass per unit area per unit time (eg. g/m^2/year)

Factors affecting (ie. limiting factors) plant productivity/ the rate of photosynthesis:

• temperature
• light intensity
• carbon dioxide concentration

Question 8

Biological yield

Answer 8

biological yield = the total biomass of plant produced

Question 9

Economic yield

Answer 9

economic yield = the total biomass of desired product produced by a crop

Question 10

Harvest index

Answer 10

Harvest index = dry mass of economic yield/ dry mass of biological yield (x100 to obtain percentage)

gives indicator of how much is wasted during the growth of a crop/ to calculate proportion of the entire crop which is usable

Question 11

Selective breeding

Answer 11

Selective breeding is a way of manipulating heredity to produce new and improved cultivators of plants/ breeds of animals that will provide a sustainable source of food for humans

Question 12

Beneficial inheritable characteristics

Answer 12

includes:

• higher yield
• higher nutritional value
• resistance to pests
• resistance to diseases
• ability to withstand extreme environmental conditions

Question 13

Variation

Answer 13

can be either:

• continuous (varying from one extreme to another)
• discrete (divides members of a species into select groups - usually controlled by alleles of a single gene)

Question 14

True breeding

Answer 14

when two organisms that have identical homozygous genotypes breed and produce an identical homozygous offspring

usually happens through self-pollination or inbreeding

Question 15

Test cross

Answer 15

A test cross can be used to:
- determine the genome of an organism: cross carried out between an organism whose genome for a certain trait is unknown and one whose homozygous recessive for that trait

Question 16

Plant field trials

Answer 16

A plant field trial is an investigation set up to:

• compare performance of two different plant cultivators under the same set of conditions
• find out the effects of different environmental conditions on a new cultivar of crop plant

Factors that must be considered includes:

• selection of treatment (only one variable should be altered)
• number of replicates (to minimise experimental error at least three replicates must be carried out - the more replicates the more reliable the results)
• randomisation of treatments (minimises bias)

Question 17

Outbreeding

Answer 17

Outbreeding involves the fusion of two gametes from unrelated members of the same species (random, maintains variation)

(e.g. wild animals, cross-pollinating plants)

Question 18

Inbreeding

Answer 18

Inbreeding involves the fusion of two gametes from close relatives

(e.g. self-pollinating plants)

Effects of inbreeding:

• loss of heterozygosity (therefore development of homozygosity)
• inbreeding depression (accumulation of recessive deleterious homozygous alleles)

Question 19

Crossbreeding

Answer 19

Crossbreeding allows new alleles to be introduced into a plant or animal species

Back crosses are carried out by crossing the new organism with the desired phenotype with an organism with the same genotype as its parents (this dilutes any unwanted characteristics)

Question 20

Hybrids

Answer 20

Hybrids are individuals that result from cross breeding two genetically dissimilar parents

F1 generation are more likely to have better vigour ‘hybrid vigour’, yield, fertility.
F2 generation tends to be too genetically diverse and lack many of the improved characteristics

Hybridisation (mating) of two different inbred homozygous cultivars of plant species produces offspring who are uniformly heterozygous

Question 21

Genetic technology

Answer 21

Genetic technology can be used to improve cultivars or breeds for commercial gain

Genetic sequencing techniques can be used to identify organisms that possess particular alleles for a desired characteristic

Genetic transformation is the transfer of genetic information from one organism to another (enhances characteristics)

Question 22

Monoculture

Answer 22

Monoculture is the agricultural practice of planting only one species of crop plant in a specific area

Monoculture competition can be reduced by growing plants in rows (however weeds will likely fill these gaps)

Question 23

Weeds

Answer 23

Weeds are any kind of plant that grows where it is not wanted

Economic impact of weeds (reduces crop plant numbers by):

• compete for resources
• release chemical inhibitors into the soil
• contaminate grain crops with their seeds (reducing crop’s value)
• acts as a host for crop pests/ diseases

Question 24

Types of plants

Answer 24

Annual plants:

• complete their entire life cycle (seed -> death) in one year
• short lifecycle - grow very quickly
• produce vast number of seeds
• seeds are viable for long periods of time

Perennial plants:

• lives for several years (dormant in winter, growing in spring)
• already established in the habitat
• have storage organs to provide food when conditions are poor
• reproduce vegetatively (asexually)

Question 25

Pests

Answer 25

Pests can be either: - nematode worms - molluscs - invertebrate pests Invertebrate pests destroy the leaves of plants, reducing its ability to carry out photosynthesis and therefore its ability to produce sugar. This leads to a reduction in the plant's vigour and yield.

Question 26

Pathogens

Answer 26

Pathogens can be either bacteria, fungi or viruses Plant diseases are caused by pathogens and can be spread throughout he air, soil or by invertebrate vectors. Plant diseases can decrease the yield of crops and can make them less marketable (e.g. cause blemishes, make them degrade too quickly)

Question 27

Control of weeds, pests and diseases

Answer 27

CULTURAL control: - ploughing, buries weeds deep enough they die and decompose - weeding, early removal of weed to reduce competition (and reduce breeding grounds for pathogens) - crop rotation, swaps which nutrients are being taken out of the soil (having a leguminous plant in the rotation means it can replace missing nutrients in the soil) CHEMICAL control: - herbicides, (a) selective, speeds up metabolism, only works on broad leafed plants (b) systemic, absorbed by plant and quickly transported throughout, kills roots and leaves (c) contact, kills all green plant tissue/ above ground leaves, roots survive so plant can regrow - pesticides, (a) systemic, absorbed by plant and quickly transported throughout, kills invertebrate when they ingest plant material (b) control, kills invertebrates when they come in contact with it, some leave protective residue which kills future invertebrates - fungicides (a) systemic, absorbed by plant and quickly transported throughout, kills fungi that attacks the plant (b) contact, kills fungi as soon as the spores germinate, can be easily washed away by the rain so must be reapplied ideal characteristics of a plant control chemical: - specific to the pest concerned - have a short life, won't bioaccumulate (build up of chemical along the food chain), will biodegrade - safe for other humans/ animals - cheap

Question 28

Biological control

Answer 28

Biological control is the control of a pest species through the introduction of one of its natural 'enemies', either a: - preditor - parasite - pathogen Biological control works best in 'closed systems' (e.g. greenhouse) so the control agent cannot escape into the wider environment, as if this does happen they could increase rapidly and cause a decrease in numbers of local populations

Question 29

IPM

Answer 29

Integrated pest management, IPM, uses a combination of biodegradable chemical, biological, cultural methods and plant resistance to improve yield Aimed to reduce us of damaging chemicals

Question 30

Providing livestock with good environmental conditions, involves...

Answer 30

- costs (housing, food, medicines) - benefits (successful breeding, increased yield) - ethics (better quality of life)

Question 31

Behavioural indicators of poor conditions

Answer 31

- stereotypy.. repetitive movement - misdirected behaviour... normal behaviour is directed inappropriately (e.g. overgrooming) - failure of sexual/ parental behaviour... failure of animals to breed successfully or lead to offspring being rejected - altered activity levels... such as excessive sleeping or hyper-aggression

Question 32

Ethology

Answer 32

Ethology is the study of animal behaviour, carried out by producing an ethogram (list of all behaviours shown by the animal) Can be studied to establish an animal's preference for certain conditions (via preference test) or to measure its motivation (reward/ punishment)

Question 33

Symbiosis

Answer 33

Symbiosis is an ecological relationship between organisms of two different species that live in direct contact with one another (intimate relationships, co-evolution... evolved over millions of year) Types: PARASITISM - the parasite derives its nutrition from the host, exploiting it by harming/ causing the loss energy or materials - parasites often have a limited metabolism and cannot survive outside the host - one benefits and on is harmed ``` MUTUALISM can be: (1) both organisms provide a service (2) one organism provides a service and another receives a resource (3) both organisms receive a resource ```

Question 34

Parasites

Answer 34

Parasites can be either: - obligate... can survive with a host - facultative... can survive with or without a host Transmission of parasites: (1) direct physical contact (2) release of resistant stages... able to survive adverse environmental conditions until they come in contact with a new host (3) use of a vector... is carried between hosts using an intermediate 'vector' Parasitic life cycles: (1) Direct life cycle... where eggs shed and pass on to a new member of the host species (2) Indirect life cycle... in addition to using a primary host species as the site for its sexual reproduction, the parasite becomes adapted by evolution to employ a secondary host species (host that is used for a short time) in its life cycle

Question 35

Symbiotic origin of chloroplasts and mitochondria

Answer 35

Chloroplasts and mitochondria are thought to have evolved from two different types of prokaryotic cells that had initially become residents in larger anaerobic cells

Question 36

Social hierarchy

Answer 36

The social hierarchy system is where the members of a social group are organised into a rank resulting from displays of ritualised threat (teeth bared, head and ears raised, eyes staring) and submissive gestures (teeth covered, head ears and tail lowered, eyes averted) between different members of the group Advantages: - aggression between members is ritualised, fighting and serious injury is avoided - experienced leadership is guaranteed - stronger, fitter members will have a better chance of pass their genes onto the next generation - protection - easier to catch prey - help raising young

Question 37

Cooperative hunting

Answer 37

Predatory mammals tend to hunt in groups to increase their hunting success Techniques include: - ambushing... involves driving the prey towards other group members that are hidden and ready to attack - members take turns running down prey to the point of exhaustion then attack Advantages: - ensures all group members are fed - can tackle larger prey, so gain ore food than hunting alone - minimises injury and energy usage

Question 38

Social mechanisms of defence

Answer 38

Social mechanisms of defence includes: (1) 'safety in numbers' - more protection - harder for predators to pick out one animal from the rest - defence formation (e.g. males form defensive ring with females and young in centre)

Question 39

Altruism

Answer 39

Altruistic behaviour is unselfish behaviour which harms the donor but benefits the recipient Types: (1) Reciprocal altruism... - an organism giving help to another in the prospect of the favour being returned (2) Kin selection... - individuals reduce their net lifetime production of offspring in order to help raise their relative's offspring - can lead to extreme altruism of the workers of some social insects

Question 40

Social insects

Answer 40

Complex social behaviour of insects includes: (1) Divison of labour... - food gathering ad defence (by numerous sterile members) - reproduction (by a few fertile individuals)

Question 41

Keystone species

Answer 41

Keystone species are important in maintaining ecosystems (e.g. the role of bees in pollination)

Question 42

Primates

Answer 42

Primates are: - placental mammals - invest a long time in parental care (allowing offspring to learn complex social behaviours required for survival) - offspring are most helpless when first born - playing allows juveniles to practice adult social behaviour - live in social groups and carry out complex social behaviours such as ritualistic display (saves energy, prevents injury) and appeasement (demonstrates understand of another member as dominate and releases tension, via appearing small, vulnerable, inferior) to prevent conflict

Question 43

Extinction

Answer 43

Extinction is the complete demise of a group of organisms Mass extinction is often a result of natural catastrophes. Afterwards, biodiversity has regained slowly due to the speciation of survivors Extinction rate measures number/ percentage of species that become extinct in a given area per unit time

Question 44

Biodiversity

Answer 44

Biodiversity is the total variation of organisms present on earth Biodiversity has three measurable components: (1) genetic diversity... - number of different alleles that exists in a population and how frequently they occur (2) species diversity... - can be split into species richness (number of different species in an ecosystem) and relative abundance (number of individuals of each species in an ecosystem) - high species diversity results in a stable ecosystem (3) ecosystem diversity... - is the number of distinct ecosystems within a defined area Maintaining biodiversity is important as: - it provides us with resources, foods, medicines - maintains important ecological process (e.g. oxygen production) - important for aesthetics, recreation (e.g. camping, fishing), and ethics (i.e. conservation for future generations)

Question 45

Habitat

Answer 45

A habitat is the area an organism lives in Habitat fragmentation: - when the original habitat is split up into several segments - can be caused by geological processes or human activity - when fragments are created the area of the habitat edges increases so species that live on the fringes of the habitat increase in population size, the area of the habitat core decreases so species that live in the centre of the habitat decrease in population size - barrier created can lead to speciation Habitat corridors: - counteract the effect of habitat fragmentation - allows re-colonisation, mating, feeding, territorial behaviour Habitat islands are habitat areas surrounded by unsuitable habitat

Question 46

Exploitation

Answer 46

Exploitation: make the best use of a resource Overexploitation: using a resource at an unsustainable rate. Reduces population size and consequently reduces its genetic variation. If over-exploitation is halted rapidly (e.g. by limiting the amount of resource being used - laws, moratorium - completely ban) then populations can recover The bottleneck effect: When a significant percentage of a population is killed or otherwise prevented from reproducing (e.g. from overexploitation), it results in a loss of genetic variation, meaning the population has a lesser ability to adapt to a changing environment/ incidence of disease.

Question 47

Species types

Answer 47

Indigenous species: native species that have always been in the geographical location they are found in Introduced (non-native) species: species that humans have moved to new geographical locations, either intentionally or accidentally Naturalised species: non-native species that become established within wild communities Invasive species: groups of naturalised species that have spread rapidly and eliminated native species - successful as: lack of natural predators/ pathogens/ parasites/ competitors, abundance of prey/ food items

Question 48

Climate change

Answer 48

Greenhouse effect: Greenhouse gases (carbon dioxide, methane) create a layer in our atmosphere that acts as an insulator, preventing heat energy from escaping and warming the planet. Contribution to greenhouse gases: - deforestation - burning fossil fuels Effects: - change in distribution and abundance of species - change in timing of season - habitat loss - increased sea level and sea temperature - migratory species leaving breeding areas earlier in the year